Dragon Ball movies are a special category of anime movie. There are a lot of them, for one, so every fan of the series can find something they love in at least one of them. They also tend to have some of the best villains in the series proper, with heavy hitters like Broly and Cooler having a special place in the fandom's heart. Most of the movies usually contain some elements of the previous sagas that would have just wrapped up or contain callbacks to big moments. The Lord Slug movie even has a glimpse of the future with a reference to the impending Super Saiyan transformation despite referencing King Piccolo aggressively.
Source：https://www.cbr.com/dragon-ball-super-hero-piccolo-important/
